A powertrain of a vehicle is known to include a transmission which changes torque and/or the number of rotations (i.e., rotation speed) of a driving apparatus including, for example, an engine and/or an electric motor, which is used for driving a driving wheel, so that the torque and/or rotations are transmitted to the driving wheel depending on driving conditions of the vehicle. There are some types of transmissions including, for example, a normally-meshed type transmission. For example, a known normally-meshed type transmission includes plural idler gears, each of which is fitted to or provided at a rotary shaft connected to the driving wheel so that the idler gear is rotatable relative to the rotary shaft and is not movable in a direction of a rotation axis thereof, and plural gears, which are provided around a periphery of a counter shaft arranged to be parallel to the rotary shaft. The idler gears and the gears normally mesh with each other. According to the known normally-engaged type transmission, a sleeve that is spline-fitted to the rotary shaft to be movable in the direction of the rotation axis is arranged side by side with the idler gear. Engaging teeth (spline), which are provided at a joining surface of the sleeve that is joined to the idler gear, are brought to be engaged with engaged teeth (dog clutch teeth) that are provided at a joined surface of the idler gear. Thus, the idler gear engaged with the sleeve and the rotary shaft integrally rotate with each other. The idler gear which rotates integrally with the rotary shaft and the gear of the counter shaft which meshes with the idler gear rotate in association with each other so that torque and/or the number of rotations of the rotary shaft is transmitted to the counter shaft. A shifting operation is performed by selecting, from among the plural idler gears including different numbers of teeth from each other, the idler gear that is to be rotated integrally with the rotary shaft and by bringing the sleeve into engagement with the selected idler gear. Depending on a timing at which the sleeve is pressed against the idler gear, there may be a case where the sleeve and the idler gear fail to engage with each other properly.
In order to bring the sleeve and the idler gear to be engaged with each other in a case where the sleeve is not properly engaged with the idler gear, according to JP3709955B which will be hereinafter referred to as Reference 1, torque with which the sleeve is pushed against the idler gear is once reduced, and thereafter the sleeve is pushed against the idler gear again with a large torque so as to properly engage the sleeve and the idler gear with each other.
According to Reference 1, in a case where the sleeve is not brought into engagement with the idler gear, only an engagement operation is performed again. Therefore, without starting the shifting operation from the beginning, the sleeve and the idler gear are brought into engagement with each other.
According to an electronic shifting apparatus disclosed in JP06-50413A which will be hereinafter referred to as Reference 2, in a case where the shifting to a desired shift position is not obtained, output for shift position change is cut off for a predetermined time period. Thereafter, the output for shift position change is again turned on. Therefore, a sufficient time for switching of a hydraulic switch valve is obtainable. The shifting may be securely performed in a case to be again performed, thereby improving operability of the transmission.
According to a shifting control method disclosed in Reference 1, a timer is used for determining that the sleeve is unable to be brought into engagement with a dog clutch of the idler gear. In a case where the sleeve does not reach a predetermined engagement position after an elapse of a predetermined time period, a reentry control is performed for again bringing the sleeve to engage with the idler gear. Thus, a control end time before the start of the reentry control, which is set by the timer, needs to be set at a value that is equal to or longer than a period of time during which the sleeve moves to the predetermined engagement position properly (that is, the period of time during which the sleeve is brought into engagement with the dog clutch without being bounced back by the dog clutch). Accordingly, at a time point at which it is determined that the sleeve is unable to engage with the dog clutch of the idler gear, the dog clutch is already pushed against the sleeve, and thus a difference in the number of rotations between the sleeve and the idler gear is small. Therefore, it takes time for the sleeve and the idler gear to come to the next position at which the sleeve and the idler gear are engaged with each other. Alternatively, it takes longer time for the sleeve and the idler gear to engage with each other next because the sleeve and the idler gear co-rotate with each other. As a result, a time for the shifting operation may be long.
According to the electronic shifting apparatus disclosed in Reference 2, in a case where the shifting to the desired shift position is not achieved, i.e., engagement is not achieved, a timer is used for cutting or turning off the output for shift position change for a predetermined time period and thereafter again turning on the output for shift position change. The shifting operation is waited until a retry counter by the timer is counted up, for example, which may result in a long period of time for determining that the sleeve is unable to engage with the dog clutch. As a result, a time for the shifting operation may be long.
A need thus exists for a dog clutch control apparatus for an automated transmission which is not susceptible to the drawback mentioned above.